Seed and Plant
Year:2005 | Volume:21 | Issue:3|Papers Count:13

Diversity is the foundation and raw material of plant breeding. Application of any breeding methods depend on the nature of genetic diversity and their breeding behavior. RAPD markers were used to determine the genetic diversity among 54 cultivars from Iran rice collection. Twelve RAPD markers applied in the present study, showed polymorphism. In this survey bands were counted with 500- 4000 bp nucleotide length and 78% of the bands were polymorphic. Collected data were managed to 0 or 1 according to the presence or absence of RAPD bands comparing with 1Kb Ladder as check. Statistically analyzed data by SPPS9.1 software, using UPGMA analysis method, classified rice genotypes into 6 main groups. Maximum similarity (91.7%) was found between Sadri Tonkaboni and Garibak Jafarabadi, and minimum similarity (44.8%) between Sang Tarom and TN-03-1199. Results showed that not only there is a considerable variation among the genebanks genotypes, a wide diversity was also found among the cultivars that are planting in a specific region. Such a genetic diversity can be successfully used in breeding programs.

Stripe (yellow) rust, caused yellow rust in wheat by the fungus Pucdnia striiformis f., sp. tritid is an important disease in Iran. Use of resistant cultivars is the best method to control the disease. This study was carried out to identify the virulence factors of stripe rust in eleven sites in Iran for three years (2001-2004). The trap nursery in each region was included 16 lines of standard sets and 12 near isogenic lines of yellow rust together with cultivar Bolani as susceptible check. In the flag leaf stage when the disease on susceptible check (Bolani) was 90-100S, all lines were scored for stripe rust. The data showed that, virulence for genes Yr2, Yr6, Yr7, Yr9, Yr25 and YrA was common in all areas in all three years. Virulence for the two genes YrSU and Yr10 was found only in Nahavand and Dezful in 2004. The results also showed that for genotypes Heines Kolben (Yr6), Kalyansona (Yr2), Lee (Yr7), Federation*4/Kavkas (Yr9), Moro (Yr10), Suwan92/omar  (YrSU), Yr6/6Avocet "S", Yr7/6Avocet "S", Yr9/6Avocet "S", Yrl7/6 Avocet "S", Avocet R (YrA) and TP1295 (Yr25) virulence factors are exist in some regions.

Micro propagation of some pear cultivars such as Abate Fetel, Conference, Kaiser and Williams are associated with several problems including low proliferation, rapid apical necrosis and production of low quality leaves. For overcoming these problems, evaluation of MS, QL and modified QL basal media, growth regulators (BAP and GA3) and putrescine showed that application of QL or modified QL instead of MS basal media, or increasing BAP concentration from 1 to 2 mgl-1, decreased apical necrosis of cultivars Abate Fetel and Kaiser and increased proliferation of cultivar Abate Fete!. Moreover, evaluation of type and concentration of three cytokinins, BAP, 2ip and Zeatin, and addition of pectin to the shoot cultures of all four experimented cultivars showed that combination of BAP, 2ip and 0.5% pectin in a medium based on modified QL basal salts, significantly increased proliferation of Conference cultivar and improved survival of all tested cultivars. Zeatin either with BAP or alone, improved leaf expansion and survival, and decreased proliferation of most cultivars. It is suggested that a medium based on modified QL basal salts enriched by 3% sucrose, 1 mgl-1 BAP, 1 mgl-1 2ip and 0.5% pectin and solidified by 0.6% agar improves proliferation and increases survival of apicals, and satisfactorily stimulates leaf expansion of these cultivars in vitro.

In order to study the vegetative characters, traits correlation and grain yield of eighteen spring canola genotypes in Gonbad area, an experiment was conducted at Agricultural Research Station of Gonbad during 2002-2004. The experiment was a randomized complete block design with four replications. The results of combined analysis showed that effects of year and cultivar were significant on the number of days from emergence to flowering and physiological maturity, duration of flowering, plant height and grain yield at the 1% level. Number of days from emergence to physiological maturity and plant height in the first year of experiment were more than those of the second year, because of a lower air temperature in the first year, however, grain yield and resistance to lodging characters in the second year, were more than those of the first year. The Hyola 420 hybrid produced the highest grain yield (356 kgha-1), and because of its good vegetative characters, it can be recommended for planting in the area together with Hyola 401 hybrid.

To assess the effects of planting method and seed rate on yield and yield components of rapeseed Hyola 401 hybrid in climatical conditions of Sistan, an experiment was carried out in Agricultural Research Station of Zahak in Zabol during 2000 and 2001. A split plot experiment in randomized complete block design with four replications was used. Three planting methods including liner, 50 cm ridges with two planting rows and 60 cm ridges with two planting rows were considered as the main plots and three seed rates of 5, 7 and 9 kgha-1 as the subplots. The results showed significant effect of year on 1000 seed weight, plant height, number of plants/m2 and number of siliques/m2 (α=1 %). The highest seed yield (3433 kgha-1) was obtained from liner planting method which did not differ significantly from furrow planting method. The highest seed yield (3407 kgha-1) was obtained from 9 kgha-1 seed rate treatment which was not significantly different from those of 5 and 7 kgha-1 seed rate treatments. The interaction effects of traits were not significant. Considering the means of interaction effects, the seed rate of 9 kgha-1 in liner planting method seems to be an appropriate treatment for Sistan region.

In the present study resistance of 24 advanced lines and 8 commercial cultivars of bread wheat to four pathotypes of powdery mildew was evaluated in the greenhouse. Powdery mildew isolates collected from Mazandaran, Golestan and Fars provinces in 2003 and 2004 were inoculated on 30 near isogenic lines and differential cultivars to determine their virulence structures. Four pathotypes were identified, among them, pathotypes No. 4 was the most highly virulent. To assess the resistance of the advanced lines and commercial cultivars of wheat, the first or second leaves of the seedlings grown in the greenhouse at Seed and Plant Improvement Institute, Karaj were inoculated separately with conidia of each pathotype. Inoculated plants were maintained under moisture chambers with 95-100 RH, in the greenhouse at 20 ±2oC and light period of 12 hours. Infection types of the seedlings were recorded 12 and 16 days after inoculation. The results of data analysis indicated that line N-78-8 was the most highly resistant line. Other lines such as C-73-5, M-81-B, N-80-16, N-80-14 and cultivar Hirmand were also highly resistant to four pathotypes. Lines N-79-7, N-80-1O, N-80-19, N-78-3, M-80-4 and cultivars Shiraz, Sorkhtokhm, Bolani and Zarrin were highly susceptible. The remaining lines and cultivars were moderately resistant or moderately susceptible.

In order to determine suitable harvest time of maize(Zea mays L.) hybrid single cross 704 (B73xMo17), a research was conducted for two years (2001 and 2002) in field and central seed laboratory of Seed and Plant Improvement Institue in Karaj. Seeds were harvested with 30%,25%,20% and 15%moisture contents after 143, 138, 133 and 128 days after planting, respectively. Standard germination tests were conducted for determination of viability, vigour and some related indices. Statistical analysis indicated that seed dry weight and days to physiological maturity were not affected by harvest time, but final germination percentage, normal seedling numbers, seedling dry weight, mean daily germination and speed of daily germination were affected by interaction of year and seed moisture contents. Results also indicated that seeds harvested by 30% moisture content (143 DAP) in the first year, had the highest final germination percentage, normal seedling number, seedling dry weight, mean daily germination and daily germination speed. All indices were declined by reduction of seed moisture content in both years. Simple correlation coefficients between studied indices indicated that final germination percentage had positive correlation with daily germination speed, seedling fresh and dry weight, and negative correlations with mean germination time. Regression analysis showed first order linear relationship between final germination percentage and seedling dry weight and normal seedling number. These results suggest that the suitable seed harvest time for hybrid maize SC704 was after seed physiological maturiy when seeds reached 30% moisture contents.

To study the effects of drought and salinity stresses on agronomical and physiological traits of five spring barley cultivars, three separate experiments using randomized complete block design with five replications were carried out under irrigated, drought and salinity stresses conditions in Miandoab Station at Agricultural Research Center of Western Azerbaijan Province in 2001-02 growing season. Results showed that, grain yield and its components, flag leaf relative water content and relative water loss from flag leaf, electrical leakage and K+/Na+ ratio were decreased under stresses conditions, while Na+ and K+ accumulation ions, proline synthesis and soluble sugars in flag leaf were increased. Faize cultivar had the highest grain yield, and Arigashare and Gorgan had the lowest yield under drought and salinity conditions, respectively. Under salinity stress Faize cultivar had lower value of Na+ ion, higher amount of K+ accumulation in flag leaf and high ratio of K+/Na+ compared to those of Arigashar. Faize compared with Arigashar had also higher value of membrane stability. Arigashar cultivar had higher water loss, higher proline synthesis and higher soluble sugars than Faize cultivar. Correlation coefficients between traits revealed that number of spike per square meter had a significantly positive correlation with grain yield under drought and salinity conditions, therefore this trait could be used as an indirect criterion for selecting high grain yield genotypes under drought and saline conditions.  

Cucurbit wilt disease caused by Phytophthora drechsleri is one of the most important diseases of cucumber. Disease severity can be decreased by plant nutrition management, especially nitrogen, phosphorus, potassium and calcium levels. For this purpose, interaction between plant nutrition and cucurbit wilt disease in some cucumber cultivars was studied in growth chamber. Different levels of N, P, K and Ca on three current cultivars (Tezier, Super 2000 and D.S.A) of cucumber were investigated at the presence of Phytophthora drechsleri using a factorial analysis based on completely randomized design with three replications. Significant differences were observed among the different levels of elements used in this study. Increase in nitrogen levels (20 meq/lNPO3-) and decrease of calcium levels (0 meq/lCa++), increased the susceptibility to the disease in plants, whereas increasing of phosphorus (4meq/lH2PO4+) and potassium (9 meq/lK+) levels decreased the susceptibility to the disease. The effects of different levels of N, P, K and Ca were also investigated on growth of P. drechsleri in vitro at a completely randomized design with three replications. Variance analysis of growth area of the fungus showed significant differences among different levels of the elements. The highest area growth of fungus was occurred at 0.1 gr/l of KCI and Ca (NO3)2(44.15 and 43.15 cm2), respectively. The factors investigated, clearly suggested the occurrence of a wide interaction between cucumber nutrition (N, P, K and Ca) and P. drechsleri, and showed the importance of plant nutrition management for decrease of disease severity.

Low-temperature (LT) stress is one of the limiting factors causing loss of yield in cereals in cold regions of Iran. Two separate randomized complete block designs were set up for 40 wheat genotypes including 32 bread wheat and 8 durum wheat genotypes and 54 barley genotypes both in three replicates under field conditions. Lowtemperature tolerance as measured by LT50 (the temperature at which 50% of plants are killed at that temperature) was determined for 5-6 weeks cold acclimated crowns of plants grown in the field at Maragheh Agricultural Research Station, Iran in the fall of 2002. Results showed that among all the tested wheat genotypes, the most LT tolerant cultivar was Norstar winter wheat with LT50 of about -25°C from Canada. Generally, Canadian cultivars (Triticum aestivum L.) had the greatest LT tolerance with average LT50 of about -23°C followed by Iranian winter bread wheat cultivars which had cc intermediate levels of LT tolerance with average LT50 between -14°C and -17°C. Durum wheat (T turgidum) selections had the lowest levels of LT tolerance between -WoC and -14°C. In barley experiment, the maximum level of LT tolerance (LT50= -15°C) was obtained from Kold and Dobtinya winter barley cultivars originated from USA and Russia, respectively. Winter barley lines from Nebraska and Dicktoo a very short day sensitive barley also had a high level of LT tolerance among tested genotypes. Barley genotypes selected from ICARDA showed the poorest LT tolerance with less than -12°C of LT50, while Iranian new improved lines derived from crosses between Iranian and foreign genotypes selected from Seed and Plant Improvement Institute (SPII) nurseries, acclimated to a colder temperature with average LT50 of about -12°C. These results demonstrated that the LT tolerance potential of a genotype depends on the adaptability of the genotype to the environment for which it was selected or in which it was evolved. This study also showed that although LT50 method is usually used in controlled conditions, however, from the results of this study it is observed that plant samples collected from the field conditions at the appropriatetime of LT acclimation can be also used for screening of LT tolerant sources which can be used in the breeding program for improvement of LT tolerance in cereals.